1. Field of the Invention
The present invention relates to an information recording and reproducing apparatus.
2. Related Background Art
Hitherto, as a form of medium in which information is recorded using a light, various kinds of disk-shaped medium, card-shaped medium, and the like have been known. Among them, a card-shaped optical information recording medium (hereinafter, referred to as an optical card) is a small-sized and light-weighted portable medium having a large recording capacity; therefore, a large demand of this medium is expected.
In the above optical card, a recording signal is modulated in accordance with recording information, a laser beam focused to a microspot scans the optical card, thereby enabling information to be recorded as a recording pit train which can be optically detected.
As an apparatus for recording and reproducing information into/from a card in this manner, an apparatus disclosed in U.S. patent application No. 810,747 has been applied.
An optical recording and reproducing medium (hereinafter, referred to as an optical card), in particular, an unerasable write-once type optical card has dimensions corresponding to a credit card size and has a large memory capacity. The dimensions of such a card are about 85 mm.times.55 mm. Now, assuming that an information track pitch is 20 .mu.m and a recording length of one bit is 5 .mu.m, EQU number of tracks=55 mm.times.(1000.div.20)=2750, EQU bit capacity/track=85.times.(1000.div.5)=17000 bits, EQU byte capacity/track=17000.div.8.apprxeq.2000 bytes.
Therefore, the whole data capacity is EQU 2750.times.2000=5,500,000=5.5 MB.
In order to manage information of such a large capacity, it is necessary to take a measure to manage recording information by directories similarly to a floppy disk. A directory is information indicating at which position which data is recorded. However, in the case of a write-once type recording medium in which information is recorded in a single direction for the arranging direction of tracks, directory information is hidden between data tracks, so that it is difficult to extract only a directory.
Moreover, in the case of forming information tracks by reciprocating a card, there is a problem such that it is difficult to control. Therefore, it is hard to provide a plurality of independent information recording sections for a single track.
To eliminate the foregoing drawbacks, in Japanese Patent Application No. 121453/1985, there has been disclosed a method whereby directory information and data to be recorded are separately recorded from a track having a small track number and from a track having a large track number. However, in this method, since a directory area in one track is not divisionally managed, there is a fear such that it is difficult to search an unrecorded area when a directory is written.